• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.348.2-348
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• 2001

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.5
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• pp.353-363
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• 2017

The dynamics of a water-steam system in a once-through boiler was simulated based on the physics-based modeling approach, representing the system in response to large load change or scale disturbance simulations. The modeling considered the mass, energy conservation, and momentum equation in the water pipe and the focus was limited to the sub-critical pressure region. An evaporator tube modeling was validated against the reference data. A simplified boiler system consisting of economizer, evaporator, and superheater was constructed to match a 500 MW power boiler. The dynamic response of the system following a disturbance was discussed along with the quantitative response characteristics. The dynamic response of the boiler system was further evaluated by checking the case of an off-design point operation of the feedwater-to-fuel supply ratio. The results re-emphasized the significance of controlling the feedwater-to-fuel supply ratio and additional design requirements of the water-steam separator and spray attemperator.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.460-474
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• 2023

A simple but accurate mathematical model is crucial for dynamic simulations and controller design of helical coil once-through steam generator (OTSG). This paper presents a three-region movable boundary dynamic model of the helical coil OTSG. Based on the secondary side fluid conditions, the OTSG is divided into subcooled region (two control volumes), two-phase region (two control volumes) and superheated region (three control volumes) with movable boiling boundaries between each region. The nonlinear dynamic model is derived based on mass, energy and momentum conservation equations. And the linear model is obtained by using the transfer function and state space transformation, which is a 37-order model of five input and three output. Validations are made under full-power steady-state condition and four transient conditions. Results show good agreements among the nonlinear model, linear model and the RELAP5 model, with acceptable errors. This model can be applied to dynamic simulations and controller design of helical coil OTSG with constant primary-side flow rate.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.11
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• pp.5405-5408
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• 2012

Curcumin (CM), a biphenyl compound, possesses anti-inflammatory, antioxidant and antimicrobial activity. MicroRNAs (miRNAs) are small noncoding RNAs which regulate gene expression and the molecular mechanisms of several biological processes. Liver fibrosis is a major cause of hepatic dysfunction and cancer and there are few effective therapies emphasizing the need for new approaches to control. The present study was conducted to investigate the effect of curcumin (CM) on liver fibrosis through modulating the expression level of miRNAs (199 and 200), the main miRNAs associated with liver fibrosis. Induction of liver fibrosis by carbon tetrachloride ($CCL_4$) was confirmed by histopathological examination. Mice were divided into 3 groups: group 1 were i.p injected with 10% $CCL_4$ twice weekly for 4 weeks and then once a week for the next 4 weeks followed by 4 weeks with olive oil only. Group 2 were i.p injected with 10% $CCL_4$ twice weekly for 4 weeks and then once a week for the next 4 weeks followed by curcumin (5 mg/mouse/day) once daily for the next 4 weeks. The third group was injected with olive oil. The expression level of miR-199 and miR-200 and some of their targeted genes were measured by real time PCR. miRNA (199 and 200) levels were significantly elevated in liver fibrotic tissues compared to control groups. Curcumin was significantly returned the expression levels of mir-199 and -200 with their associated target gene nearly to their normal levels. This is the first study that highlighted the effect of curcumin on liver fibrosis through regulation of miRNAs.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.807-808
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• 2005

• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.530-531
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• 2005

• The Journal of Society for e-Business Studies
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• v.6 no.2
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• pp.13-24
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• 2001

The Real-Time Best-Estimate simulator NPA4K is being developed for providing an efficient nuclear power, KALIMER, simulation environment for transient safety analyses using information visualization. The advanced features of NPA4K simulator are the Once-Through Running Environment, Functionalities of displaying the several X-Y Plot on one system, and Multi-thread Processing, The objective of NPA4K simulator is ta realize the Virtual Reality Environment through Network and Internet technology in Nuclear Power Plants.

• Architectural research
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• v.15 no.3
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• pp.167-174
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• 2013

Due to increasing competition of construction companies, it is required to optimize the management of construction projects and "lean" concepts are rapidly spreaded in construction industry. Steel work accounts for a large proportion in construction work, and a variety of attempts to efficiently perform steel work has currently made. And since rebar (Engineer-to-Order) can be engineered through design once order is placed, it gives the great impact on construction, thus, entire management is required. The purpose of this study is to present the method to increase the efficiency of field processing method of steel work in terms of lean construction. Once we examine process of steel work and identify the flow, we would like to analyze which processes should be improved through value analysis approach and present the improvement plans. Also, this study examines cases of field processing and factory processing, and it identifies the waste factors in the procurement process. Finally, this study would like to present the result of analysis from the perspectives of value. The rebar delivery process is divided into several steps and the duration of every step is surveyed. Using duration data, VAT (Value added time) can be calculated for analyzing the efficiency of the process.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.11-18
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• 2022

In this research, curium oxide (CmO₂) is studied as fuel for VVER-1200 reactor to get an attention to its energy value and possibilities. For this purpose, CmO₂ is used in fuel rods or integrated burnable absorber (IBA) rods with and without UO₂ and then compared with the conventional fuel assembly of VVER-1200 reactor. It is burned to 60 GWd/t by using SRAC-2006 code and JENDL-4.0 data library. From these studies, it is found that CmO₂ is competent like UO₂ as a fuel due to higher fission cross-section of ²⁴³Cm and ²⁴⁵Cm isotopes and neutron capture cross-section of ²⁴⁴Cm and ²⁴⁶Cm isotopes. As a result, when some or all of the UO₂ of fuel rods or IBA rods are replaced by CmO₂, we get a similar k-inf like the reference even with lower enrichment UO₂ fuels. These studies show that the use of CmO₂ as IBA rods is more effective than the fuel rods considering the initially loaded amount, power peaking factor (PPF), fuel temperature and void coefficient, and the quality of spent fuel. From a detailed study, 3% CmO₂ with inert material ZrO₂ in IBA rods are recommended for the VVER-1200 reactor assembly from the once through concept.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2395-2406
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• 2023

To study the influence of parameter uncertainty in small pressurized water reactor (SPWR) once-through steam generator (OTSG), the nonlinear mathematical model of the SPWR is firstly established. Including the reactor core model, the OTSG model and the pressurizer model. Secondly, a control strategy that both the reactor core coolant average temperature and the secondary-side outlet pressure of the OTSG are constant is adopted. Then, the uncertainty quantification method is established based on Latin hypercube sampling and statistical method. On this basis, the quantitative platform for parameter uncertainty of the OTSG is developed. Finally, taking the uncertainty in primary-side flowrate of the OTSG as an example, the platform application work is carried out under the variable load in SPWR and step disturbance of secondary-side flowrate of the OTSG. The results show that the maximum uncertainty in the critical output parameters is acceptable for SPWR.